I went through the whole tire psi. thing years ago. sure 55 psi may feel OK, but what I settled on and what many others have found is that pressures between 65 and 80 are the best setting for an "E" rated tire. at my pressures of 75 frt and 80 rear the tires last a very long time, have no abnormal wear and the X is very stable. I`ve driven at speeds of 65-70mph for up to 12 hours in upper 90`s towing my 9200lb TT. I`ve even had to make an emergency lane change at 65mph, I hesitate to think how that would've played out if the tires were at 55psi!


Please rethink your pressures! you`ll be glad you did.

 

That's not correct. At 35 PSI that tire is rated for 2,755 lbs, or 5,510 per axle. Loaded to GVWR none of your axles are that heavy. You're applying your logic as if it were the factory tire size. Pressure works by surface area; his larger tires have greater surface area so they need less pressure to safely hold up the truck.

I've done that with my old Ex at the recommended 45/55 PSI and it did just fine. Vehicle stability is tested at recommended pressures by the engineers who designed it. What do you know that they don't?

 

Without knowing your tire size 65-80 psi is a meaningless number.

The "E" haThe "E" rating has nothing to do with how much air pressure is Required.

All I can deduce from an E rating @80 psi is either your excursion weight is.
4000 +\- pounds beyond the GVWR Or you are over inflating your tires.

 

The difference is more than a pressure rating! It has to do with plys and sidewall thickness. Believe me, the more psi the better. I'm towing a 9200lb TT and yes......low pressure makes a huge difference in how the X (or any vehicle) handles! And no the tires are not overinflated! They are inflated to the proper pressure for handling and safety, not he bare minimum required for a soft ride. If I wanted a soft ride and mushy handling i'de be driving a GM truck!

 

I Like your diliberate miswriting .
But now my 2 cents.
Call myself tirepressure-specialist nowadays, and the story began with the official european formula I got hold of , and went running with.

Tire pressure advice is to give the tire a deflection for the speed , at wich no part of the rubber gets to hot it hardens, and damages in next bendings/deflection.

So if you can produce exact weights on seperate wheels in the situation you drive with ,I can calculate a needed pressure. But also need the maximum you drive and wont go over for even a minute.

But this determining the loads on tires is the hardest part.

Once you have that , you only need the to natures laws right calculation.
And the American calculation is not .
For Standard load and XL/reinforced/Extraload P-tires, America stepped over to the better European calculation ( but not yet perfect) as late as 2006 ( after the Ford/Firestone affaire was forgotten),
Europe used this calculation and still does, for every kind of tire from SL to H-load truck tires.

But to my opinion this wrong american calculation was not the main cource of the failures of the Firestone tires wich courced roll over accidents and more then 100 death people , so no yoke. this was repaired for SUV by substracting 10% of the maximum load when using P-tires .
To my opinion, the large profile blocks that cover part of the sidewall, and makes this sidewall less flexible so more heatproduction.
The maximum load was calculated as if it was a normal road tire, and still is done nowadays.
Higher pressure will give lesser deflection so lesser heatproduction and no tire-damage.


For LT tires America still uses a formula that leads to to much deflection.
Checked the list given by Country Mouse and its made with that calculation .
If it would be made with European calculation it would lead to lower loadcapacity's for the pressure.
I am using now my own formula based on an article I read from an American IR J.C.Daws, wich leads to even lower loadcapacity's.

To make this already to long story short, TS try to determine weights and give exact tire data and I will calculate.
But for the moment , when towing , only rear tires need higher pressure, front is mostly even lifted up a bit by leaver working.
Even when using a weight distibution hich , wich only transports a part of the load from rear tires to front car tires and Trailer tires.

Greatings from a Dutch Pigheaded Self-declared Tirepressure-Specialist.
Peter

 

I was just rereading some of the posts. The 80 psi is for cold fill. The manuf of the tire already allowed for expansion, which isn't much more than 5 psi if that! Otherwise it would state as such.

You really should listen to those of us that tow heavy trailers regularly. we have the miles and knowledge to point you in the right direction. I can sit here and type things without actual knowledge of the subject all day long, but I would rather take the word of people towing for thousands of miles a year rather than someone that tows a small utility trailer around town.

The door sticker for pressures was based on "D" rated tires, because they offered the softest ride for the soccer moms the X was aimed at. This made hem handle like crap and why they swapped them to load range "E"'s. I know of many E and F250,350's that have a door sticker for pressures of 65-80psi. It's because they knew they would be used for heavy loads.

I will stick by my 75 frt and 80 rear pressures!

 

You might be towing 9200 pounds but not all of that 9200 is not being supporting by the air pressure in your excursions tires.

The psi in your tires supports the weight they are holding up not pulling.

The weight that you need to use to determine your psi is the vehicle weight.
IN the case of towing that will be the curb weight + cargo weight + trailer tongue weigh.

The easiest way to find out the weight on each axle is to stop at a scale and have each axle weighted. They will give you front axle, rear axle and trailer weight axles.

 

Sweet,

I can sit here and post about things I have considerable knowledge on AND I can back them up with facts from reliable souces.

 

No, actually the door certificate psi is based on tire size and the vehicles GVWR.

The required Psi doesn't change depending on D or E rating it changes according to tire size and vehicle weight.

 

I would be interested in a controlled test of identical tires ran at door sticker psi vs sidewall psi while running at max weight. A test that ran the tire to failure either from tread wear or absolute failure. Which would last longer? Which would heat up more and break down faster?

 

Yes, many people don't understand that low psi (even recommended psi) will heat a tire up faster and hotter than a tire run at a higher psi.

I guess some people are book smart and others are street smart. And Some people are just so adamant about something they don't understand how things work in the real world!

 

And now your ignorant side is showing! Picking and choosing parts of a sentence to quote! There goes any credibility you may have thought you had!

Now I'm done arguing about this. I won't be adding in or trying to offer any more useful info.

Good luck!

 

This is getting a bit silly IMHO.

If you want to run your tires at the max, knock yourself out. If you want to follow what the engineers at every tire company and vehicle manufacturer recommend, you should do that too. As long as you don't go below this the world will not end. I could go on and on about my experience and what I've towed and the associated tire pressures, but at that point I'd just be prolonging the pissing contest.

 

Agreed, plus these threads (of which ONLY a very few qualify) make me think all about Brent..

 

I assume as a random nobody posting on an internet forum I have no credibility in the first place. That is why I added the part about backing up my statement from a credible source.

Also, its only an argument if personal attacks are being tossed about. lets have a civil conversation and discuss the the facts.